1. Field of the Invention
The present invention relates to a hydrogen supply device for producing hydrogen due to a reforming reaction of reforming material and supplying the produced hydrogen to a hydrogen consumption device.
2. Description of Related Art
Conventionally, a reforming apparatus, in which hydrogen rich gas is produced by reforming hydrocarbon compound, is well known as a device for supplying hydrogen to a fuel cell. In the reforming apparatus, the hydrogen is produced by reforming material containing hydrocarbon compound due to a catalytic reaction at high temperature (vapor steam reforming reaction). To perform the vapor steam reforming reaction, it is necessary to maintain the reforming apparatus at high temperature. A conventional method of maintaining the reforming apparatus at high temperature is to heat up the reforming apparatus in use of combustion heat based on combustion of unreacted gas (off gas containing hydrogen) emitted from the fuel cell.
As the reforming apparatus mentioned above, there is an apparatus as disclosed in JP-A-11-343101. This reforming apparatus has a combustion chamber and a reforming chamber which are separated by an isolation wall and heat is exchanged between the combustion chamber and the reforming chamber via the isolation wall. Combustion heat generated by burning fuel (off gas) in the combustion chamber causes to heat up the reforming chamber so that reforming material flowing in the reforming chamber is reformed to a gas containing hydrogen (reformed gas) under the help of a reforming catalyst in the reforming chamber.
However, since the combustion heat generated in the combustion chamber indirectly heats the reforming catalyst disposed in the reforming chamber through the isolation wall, heat resistance is larger and temperature increase is slower so that a start timing of the reforming reaction is retarded. Further, the conventional reforming apparatus has a drawback that a harmful ingredient such as unburned components in the combustion gas is exhausted into the atmosphere without being purified, in particular, at the starting time for activation. Furthermore, it is disadvantageous to apply the conventional reforming apparatus, which needs a relatively large heat transfer surface or body to secure a required amount of the heat transfer, to a vehicle whose installation space is limited.
Moreover, though the vapor steam reforming reaction, which is an endothermic reaction and needs heat from outside, is useful to obtain rich hydrogen, the conventional heat exchanger is not sufficient enough to supply the heat. Therefore, it is very common to use a partial oxidation reforming reaction (an exothermic reaction), in which air is added to the reforming material, simultaneously with the vapor steam reforming reaction.
However, oxygen in the air is used in the partial oxidation reforming reaction for having the reforming material reacted. Nitrogen gas contained in the air causes to dilute a density of hydrogen gas so that power generation efficiency of the fuel cell is lowered. Further, it has a drawback that an amount of gas passing through the passages for fuel reforming increases with higher flowing loss and a driving force for supplying the oxygen increases, too.
Further, the conventional device for producing hydrogen in the vapor steam reforming reaction is provided on a downstream side of a reforming section with a CO eliminating section in which CO is eliminated from the hydrogen rich gas. In the CO eliminating section, a shift reaction (CO+H2O→H2+CO2) and an oxidation reaction (CO+½O2→CO2) are performed. Since the shift reaction needs moisture (vapor steam), the reforming material tends to contain the moisture whose amount exceeds the amount necessary for the reforming reaction.
Therefore, a structure of the evaporation section for evaporating and vaporizing the reforming material is larger because the moisture whose amount exceeds the amount necessary for the reforming reaction has to be evaporated and vaporized. Further, the fuel cell, to which hydrogen is supplied, emits exhaust gas containing a large amount of moisture.
Moreover, the hydrogen rich gas, which is produced in the reforming section and supplied to the fuel cell, contains impurities other than hydrogen such as nitrogen and carbon dioxide. Accordingly, a density of hydrogen contained in the hydrogen rich gas is lower so that a power generation efficiency of the fuel cell is lower.